Radio frequency identification (RFID) tags are relatively low cost wireless devices. RFID tags are typically used in tracking, identification, and communication. RFID tags include circuits that have a processor, a memory, an analog to digital converter/digital to analog converter, and an antenna. RFID tags may be classified as passive or active, where passive RFID tags rely on an external power supply and active RFID tags include a power supply. RFID tags may be attached as a “sticker” to or embedded into products, animals, and even people.
RFID tags operate in different frequency spectrums, ranging from low frequency (e.g., 125 Khz) to microwave frequency. The RFID tag frequency used typically depends on an application of the RFID tag.
Examples of applications for RFID tags include animal identification, inventory (e.g., library books, beer kegs, etc.) tracking, automobile key and lock activation (i.e., “smart key” technology), badge identification, etc. Furthermore, new applications continue to evolve using RFID tags, such as the replacement of current universal product code (UPC) tracking systems with RFID tag systems.
RFID tags may be part of a larger RFID system that can include tag readers, tag programming stations, circulation readers, sorting equipment and tag inventory wands. In general, there may be a wireless access point (WAP) such as a network interface card (NIC) that connects (i.e., allows communication between) a computing device (e.g., computer) to RFID tags.
RFID tags are full duplex devices, meaning that they are able to send and receive communications. In particular, RFID tags send and receive communications to and from WAPs of an RFID system. Although other wireless devices may be able to receive communication from RFID tags (i.e., upstream communication from an RFID tag which can either be transmitted or backscattered), these wireless devices may not be able to send communication to the RFID tags (i.e., downstream communication from an RFID tag). Examples of such wireless devices include WAPs of wireless local area networks (e.g., IEEE 802.11 based), global systems for mobile (GSM) based cellular telephones, Bluetooth enabled devices, sensor network access points, etc. For example, if an RFID tag enters a WLAN system, WAPs of the WLAN system may be able to read from (i.e., receive communications) to the RFID tag; however, the WAPs are not able to write to (i.e., send communications) to the RFID tag.